Process to continuously prepare two or more base oil grades and middle distillates

ABSTRACT

Process to prepare simultaneously two or more base oil grades and middle distillates from a de-asphalted oil or a vacuum distillate feed or their mixtures by performing the following steps: (a) hydrocracking the feed, thereby obtaining an effluent; (b) distillation of the effluent as obtained in step (a) into one or more middle distillates and a residue boiling substantially above 340° C.; (c) separating, by means of a further distillation step said residue into a light base oil precursor fraction and a heavy base oil precursor fraction; (d) reducing the pour point of each separate base oil precursor-fraction iri″two simultaneously and parallel operated catalytic dewaxing reactors obtaining a first and second dewaxed oil; (e) hydrotreating the first dewaxed oil as obtained when dewaxing the heavy base oil precursor fraction in step (d); (f) isolating from the second dewaxed oil from the light base oil precursor fraction from step (d) and the hydrotreated oil from step (e) two or more base oil grades.

FIELD OF INVENTION

The invention relates to a process to continuously prepare two or morebase oil grades and middle distillates.

BACKGROUND OF THE INVENTION

WO-A-0250213 describes a process wherein different base oil grades aremade in a so-called blocked out mode. In this process a bottoms fractionof a fuels hydrocracking process, which thus also yields middledistillates as products, is separated into various base oil precursorfractions. These fractions are subsequently catalytically dewaxed oneafter the other using a platinum-ZSM-5 based catalyst.

WO-A-9718278 discloses a process wherein up to 4 base oil grades, e.g. a60N, 100N and 150N, are prepared starting from the bottoms fraction of afuels hydrocracker. In this process the bottoms fraction is fractionatedin a vacuum distillation into 5 fractions of which the heavier 4fractions are further processed to different base oil grades by firstperforming a catalytic dewaxing followed by a hydrofinishing step.

WO-A-02/50213 discloses a so-called blocked-out process to preparedifferent base oil grades from the bottoms fraction of a fuelshydrocracking process.

A disadvantage of the above processes is that the process is notcontinuous. In other words the base oil grades are not made at the sametime but sequential. This requires tankage for the intermediate productsas obtained when the hydrocracker bottoms are fractionated and areawaiting their turn to be catalytically dewaxed. A further disadvantageare the mode switches which result in heating up of equipment andcooling of equipment causing erosion of equipment. The mode switchesalso result in intermediate off-spec product every time a new grade isbeing processed. These slops need to be reprocessed or disposed offwhich is disadvantageous.

EP-A-649896 discloses a process to prepare a residue comprising a baseoil by means of a process involving a hydrotreating step and ahydrocracking step on a heavy petroleum feedstock. The hydroprocessingsteps yield a product from which middle distillates and a bottomsfraction (residue) are obtained. This bottoms fraction is subsequentlysolvent dewaxed to a single base oil grade.

EP-A-0 272 729 discloses a process for the manufacture of lubricatingbase oils, wherein a flashed distillate produced via a residueconversion process is fed to a hydrocracking unit. The effluent from thehydrocracking unit is fed to a catalytic dewaxing unit and thereafteroptionally the whole dewaxed stream is subjected to a hydrotreatment.

WO-A-9723584 discloses a process wherein the bottoms fraction of a fuelshydrocracker is subjected to a catalytic dewaxing step. The dewaxed oilis partly recycled to the hydrocracking step and partly obtained as thelubricating base oil.

A disadvantage of the above process as described in WO-A-9723584 is thatif more than one base oil grade is isolated from the dewaxed oil a largepour point distribution occurs. In other words the resulting lowerviscous base oil grades will have a too low pour point. This pour pointgive away, or difference with the desired value, is indicative for yieldloss of said lower viscous base oil grade.

One object of the present invention is to provide a process, which iscapable of preparing two or more base oil grades simultaneously andwherein their respective pour points are more close to the desiredvalues.

It is another object of the present invention to provide an alternativeprocess.

SUMMARY OF THE INVENTION

The following process achieves one ore more of the above or otherobjects.

Process to prepare simultaneously two or more base oil grades and middledistillates from a de-asphalted oil or a vacuum distillate feed or theirmixtures by performing the following steps:

-   (a) hydrocracking the feed, thereby obtaining an effluent;-   (b) distillation of the effluent as obtained in step (a) into one or    more middle distillates and a residue boiling substantially above    340° C.;-   (c) separating, by means of a further distillation step said residue    into a light base oil precursor fraction and a heavy base oil    precursor fraction;-   (d) reducing the pour point of each separate base oil precursor    fraction in two simultaneously and parallel operated catalytic    dewaxing reactors obtaining a first and second dewaxed oil;-   (e) hydrotreating the first dewaxed oil as obtained when dewaxing    the heavy base oil precursor fraction in step (d);-   (f) isolating from the second dewaxed oil from the light base oil    precursor fraction from step (d) and the hydrotreated oil from    step (e) two or more base oil grades.

Applicants found that when processing according to the invention it ispossible to continuously prepare two or more base oil grades and at thesame time reduce the hydrotreating capacity because only the heaviergrades which require further hydrotreating are subjected to said step(e). Further any product give away in pour point may be avoided becausethe two parallel operated dewaxing reactors can be operated such thatthe pour point of the resulting low and high viscous base oil grades areclose to the desired values. Any pour point give away is indicative foryield loss of the grade having the lower than desired pour point.

DETAILED DESCRIPTION OF THE INVENTION.

The feed to step (a) may be any typical mineral crude derived feed to ahydrocracker. Such feedstocks may be the vacuum gas oil or heavierdistillate fractions as obtained when distilling at near vacuumconditions the atmospheric residue of a crude mineral oil feedstock. Thedeasphalted oil as obtained when deasphalting the residue as obtained insaid vacuum distillation may also be used as feed. Light and heavy cycleoils as obtained in a fluid catalytic cracking process (FCC), thermallyflashed distillate and aromatic rich extracts as for example obtained insolvent extraction process steps in traditional base oil processing mayalso be used as feed. Mixtures of the above described feeds andoptionally other hydrocarbon sources are also suitable as feedstocks. Anoptional alternative hydrocarbon source, which may be present inaddition to the above feedstocks, preferably in amounts of between 2 and30 wt % of the feed to step (a), are the paraffin wax as obtained in aFischer-Tropsch process. Preferably the feed to step (a) consists of amineral crude derived feed.

Step (a) may be performed at a conversion level of between 15 and 90 wt%. The conversion is expressed in the weight percentage of the fractionin the feed which boils above 370° C. which are converted to productsboiling below 370° C. The main products boiling below 370° C. arenaphtha, kerosene and gas oil. Examples of possible hydrocrackerprocesses suitable for performing step (a) are described in EP-A-699225,EP-A-649896, WO-A-9718278, EP-A-705321, EP-A-994173 and U.S. Pat. No.4,851,109.

The operating conditions of a single step hydrocracking process includepreferably a temperature in the range of from 350 to 450° C., a hydrogenpressures in the range of from 9 to 200 MPa, more preferably above 11MPa, a weight hourly space velocities (WHSV) in the range of from 0.1 to10 kg of oil per liter of catalyst per hour (kg/l/hr), preferably from0.2 to 5 kg/l/hr, more preferably from 0.5 to 3 kg/l/hr and hydrogen tooil ratios in the range of from 100 to 2,000 liters of hydrogen perliter of oil.

Preferably the hydrocracker is operated in two steps, consisting of apreliminary hydrotreating step followed by a hydrocracking step. In thehydrotreating step nitrogen and sulphur are significantly removed andaromatics are significantly saturated to naphthenes and part of thenaphthenes are converted to paraffins by ring opening reactions. Inorder to improve the yield of the more viscous grade base oils thefuels-hydrocracker is more preferably operated by first (i)hydrotreating a hydrocarbon feed at a feed conversion, wherein theconversion, as defined above, of less than 30 wt % and preferablybetween 15 and 25 wt %, and (ii) hydrocracking the product of step (i)in the presence of a hydro-cracking catalyst at such a conversion levelthat the overall conversion of step (i) and (ii) is between 15 and 90 wt% and preferably between 40 and 85 wt %.

The operating conditions of a hydrotreating step are preferably atemperature in the range of from 350 to 450° Cl., a hydrogen pressuresin the range of from 9 to 200 MPa, more preferably above 11 MPa, aweight hourly space velocities (WHSV) in the range of from 0.1 to 10 kgof oil per liter of catalyst per hour (kg/l/hr), preferably from 0.2 to5 kg/l/hr, more preferably from 0.5 to 3 kg/l/hr and hydrogen to oilratios in the range of from 100 to 2,000 liters of hydrogen per liter ofoil.

The operating conditions of a hydrocracking step performed incombination with a hydotreatings step are preferably a temperature inthe range of from 300 to 450° C., a hydrogen pressures in the range offrom 9 to 200 MPa, more preferably above 11 MPa, a weight hourly spacevelocities (WHSV) in the range of from 0.1 to 10 kg of oil per liter ofcatalyst per hour (kg/l/hr), preferably from 0.2 to 5 kg/l/hr, morepreferably from 0.5 to 3 kg/l/hr and hydrogen to oil ratios in the rangeof from 100 to 2,000 liters of hydrogen per liter of oil.

The residues as prepared by the processes as described above have a verylow content of sulphur, typically below 250 or even below 150 ppmw, anda very low content of nitrogen, typically below 30 ppmw. The residue ispreferably a full range residue.

It has been found that by performing the combined hydrotreating andhydrocracking step as described above a residue is obtained which yieldsa high quantity of the more viscous grade base oil, also referred to asmedium machine oil grade, and of acceptable quality with respect toviscosity index. In addition a sufficient quantity of naphtha, kerosineand gas oils are obtained by this process. Thus a fuels hydrocrackerprocess is obtained wherein simultaneously products ranging from naphthato gas oil and a residue is obtained, which residue has the potential toyield a medium machine oil base oil grade. The viscosity index of theresulting base oil grades is suitably between 95 and 120, which isacceptable to yield base oils having a viscosity index according to theAPI Group II specifications.

It has been found that in the hydrotreating step (i) the viscosity indexof the residue and the resulting base oil grades increases with theconversion in said hydrotreating step. By operating the hydrotreatingstep at high conversion levels of more than 30 wt % viscosity indexvalues for the resulting base oils of well above 120 can be achieved. Adisadvantage of such a high conversion in step (i) is however that theyield of medium machine oil fraction will be undesirably low. Byperforming step (i) at the above described conversion levels an APIGroup II medium machine oil grade base oil can be obtained in a desiredquantity. The minimum conversion in step (i) will be determined by thedesired viscosity index, of between 95 and 120, of the resulting baseoil grades and the maximum conversion in step (i) is determined by theminimum acceptable yield of medium machine oil grade.

The preliminary hydrotreating step is typically performed using catalystand conditions as for example described in the above-mentionedpublications related to hydrocracking. Suitable hydrotreating catalystsgenerally comprise a metal hydrogenation component, suitably Group IVBor VIII metal, for example cobalt-molybdenum, nickel-molybdenum, on aporous support, for example silica-alumina or alumina. The hydrotreatingcatalysts suitably contains no zeolite material or a very low content ofless than 1 wt %. Examples of suitable hydrotreating catalysts are thecommercial ICR 106, ICR 120 of Chevron Research and Technology Co.; 244,411, DN-120, DN-180, DN-190 and DN-200 of Criterion Catalyst Co.; TK-555and TK-565 of Haldor Topsoe A/S; HC-k, HC-P, HC-R and HC-T of UOP;KF-742, KF-752, KF-846, KF-848 STARS and KF-849 of AKZO Nobel/NipponKetjen; and HR-438/448 of Procatalyse SA.

The hydrocracking step is preferably a catalyst comprising an acidiclarge pore size zeolite within a porous support material with an addedmetal hydrogenation/dehydrogenation function. The metal having thehydrogenation/dehydrogenation function is preferably a Group VIII/GroupVIB metal combination, for example nickel-molybdenum andnickel-tungsten. The support is preferably a porous support, for examplesilica-alumina and alumina. It has been found that a minimum amount ofzeolite is advantageously present in the catalyst in order to obtain ahigh yield of medium machine oil fraction in the full range residue whenperforming the hydrocracker at the preferred conversion levels asexplained above. Preferably more than 1 wt % of zeolite is present inthe catalyst. Examples of suitable zeolites are zeolite X, Y, ZSM-3,ZSM-18, ZSM-20 and zeolite beta of which zeolite Y is most preferred.Examples of suitable hydrocracking catalysts are the commercial ICR 220and ICR 142 of Chevron Research and Technology Co; Z-763, Z-863, Z-753,Z-703, Z-803, Z-733, Z-723, Z-673, Z-603 and Z-623 of ZeolistInternational; TK-931 of Haldor Topsoe A/S; DHC-32, DHC-41, HC-24,HC-26, HC-34 and HC-43 of UOP; KC2600/1, KC2602, KC2610, KC2702 andKC2710 of AKZO Nobel/Nippon Ketjen; and HYC 642 and HYC 652 ofProcatalyse SA.

The effluent of the hydrocracker is separated into one or more of theabove referred to fuels fractions and a residue. The residue, whereinthe residue boils predominately above 340° C., is used as feed to step(c). With boiling predominately above 340° C. is especially meant thatmore than 80 wt %, preferably more than 90 wt %, boils above 340° C.Because a substantial fraction of the residue may boil in the gas oilrange a considerable amount of gas oil is recovered after dewaxinghaving excellent cold flow properties. Preferably between 10 and 40 wt %of the dewaxed oil as obtained in this process boils in the heavy gasoil range being between from 350 to 400° C. It should of course beunderstood that also lower boiling gas oil fractions are obtained instep (c).

The final boiling point of the residue will be partly determined by thefinal boiling point of the feed to step (a) and may be far greater than700° C. up to values of which cannot be determined by means of thestandard test methods.

Optionally part of the residue as obtained in step (b) may be recycledto step (a) as for example described in EP-A-0994173, which publicationis incorporated by reference. Optionally the residue may be recycled toonly the hydrocracking step of step (a) as for example described inEP-B-0699225, which publication is incorporated by reference. Preferablyless than 15 wt % of the residue is recycled to step (a) and morepreferably no residue is recycled to step (a). It has been found thatAPI Group II base oils may be prepared having a good quality withouthaving to perform such a recycle.

In step (c) the feed is separated by means of distillation into a lightbase oil precursor fraction and a heavy base oil precursor fraction andoptionally a vacuum gas oil fraction. Preferably any vacuum gas oil isnot separated from the light base oil precursor fraction but remainscombined with said fraction in order to be dewaxed as well in step (d).The distillation is suitably performed at reduced pressures, morepreferably the vacuum distillation is performed at a pressure of between0.01 and 0.3 bara. Preferably the 10 wt % recovery point of the heavybase oil precursor fraction as obtained in step (c) is preferablybetween 420 and 550° C. and more preferably between 440 and 520° C.

The feed to step (d) will comprise of the base oil precursor fractionsas obtained in step (c). Optionally some partly isomerised paraffin waxboiling in the heavy or light base oil precursor fractions boiling rangemay be present in a mixture with said light base oil precursor fraction.This paraffin product is also referred to as waxy raffinate, as obtainedin a Fischer-Tropsch or Gas-to-Liquids Process. Such a waxy Raffinatemay be prepared according the process as described in WO-02070630, whichpublication is incorporated herein by reference.

Optionally a noble metal guard bed may be positioned just upstream thedewaxing catalyst bed in the dewaxing reactor in step (d) in order todecrease the level of sulphur and especially nitrogen compounds. Such aguard bed may be especially advantageous in the dewaxing reactor inwhich the heavy base oil precursor fraction is processed. An example ofsuch a process is described in WO-A-9802503, which reference is herebyincorporated by reference.

The catalytic dewaxing step in the parallel operated reactors in step(d) can be performed by any process wherein in the presence of acatalyst and hydrogen the pour point of the base oil fraction isreduced. Suitably the pour point is reduced by at least 10° C. and moresuitably by at least 20° C. Suitable dewaxing catalysts areheterogeneous catalysts comprising a molecular sieve and optionally incombination with a metal having a hydrogenation function, such as theGroup VIII metals. Molecular sieves, and more suitably intermediate poresize zeolites, have shown a good catalytic ability to reduce the pourpoint of a base oil fraction under catalytic dewaxing conditions.Preferably the intermediate pore size zeolites have a pore diameter ofbetween 0.35 and 0.8 nm. Suitable intermediate pore size zeolites areZSM-5, ZSM-12, ZSM-22, ZSM-23, SSZ-32, ZSM-35 and ZSM-48. Anotherpreferred group of molecular sieves are the silica-aluminaphosphate(SAPO) materials of which SAPO-11 is most preferred as for exampledescribed in U.S. Pat. No. 4,859,311. ZSM-5 may optionally be used inits HZSM-5 form in the absence of any Group VIII metal. The othermolecular sieves are preferably used in combination with an added GroupVIII metal. Suitable Group VIII metals are nickel, cobalt, platinum andpalladium. Examples of possible combinations are Ni/ZSM-5, Pt/ZSM-23,Pd/ZSM-23, Pt/ZSM-48 and Pt/SAPO-11. Further details and examples ofsuitable molecular sieves and dewaxing conditions are for exampledescribed in WO-A-9718278, U.S. Pat. No. 5,053,373, U.S. Pat. No.5,252,527 and U.S. Pat. No. 4,574,043.

The process according the present invention makes it possible tocontinuously prepare base oils using dewaxing catalysts, which show arelatively large pour point distribution in case the full range residueis processed as for example described in WO-A-9723584. By making use ofthe present invention such a large pour point distribution can beavoided while using such relatively poor performing dewaxing catalysts.An example of such a catalyst that shows a relatively large pour pointdistribution is the ZSM-5 based catalyst. Thus ZSM-5 based catalysts maybe advantageously applied in the present invention. The process alsomakes it possible to use different dewaxing catalysts in theparallel-operated reactors, which catalyst can be more tailored to theirrespective feeds.

The dewaxing catalyst suitably also comprises a binder. The binder canbe a synthetic or naturally occurring (inorganic) substance, for exampleclay, silica and/or metal oxides. Natural occurring clays are forexample of the montmorillonite and kaolin families. The binder ispreferably a porous binder material, for example a refractory oxide ofwhich examples are: alumina, silica-alumina, silica-magnesia,silica-zirconia, silica-thoria, silica-beryllia, silica-titania as wellas ternary compositions for example silica-alumina-thoria,silica-alumina-zirconia, silica-alumina-magnesia andsilica-magnesia-zirconia. More preferably a low acidity refractory oxidebinder material which is essentially free of alumina is used. Examplesof these binder materials are silica, zirconia, titanium dioxide,germanium dioxide, boria and mixtures of two or more of these of whichexamples are listed above. The most preferred binder is silica.

A preferred class of dewaxing catalysts comprise intermediate zeolitecrystallites as described above and a low acidity refractory oxidebinder material which is essentially free of alumina as described above,wherein the surface of the aluminosilicate zeolite crystallites has beenmodified by subjecting the aluminosilicate zeolite crystallites to asurface dealumination treatment. A preferred dealumination treatment isby contacting an extrudate of the binder and the zeolite with an aqueoussolution of a fluorosilicate salt as described in for example U.S. Pat.No. 5,157,191. Examples of suitable dewaxing catalysts as describedabove a silica bound and dealuminated Pt/ZSM-5 and silica bound anddealuminated Pt/ZSM-23, silica bound and dealuminated Pt/ZSM-12 andsilica bound and dealuminated Pt/ZSM-22, as for example described inWO-A-200029511 and EP-B-832171.

Catalytic dewaxing conditions are known in the art and typically involveoperating temperatures in the range of from 200 to 500° C., suitablyfrom 250 to 400° C., hydrogen pressures in the range of from 10 to 200bar, weight hourly space velocities (WHSV) in the range of from 0.1 to10 kg of oil per litre of catalyst per hour (kg/l/hr), suitably from 0.2to 5 kg/l/hr, more suitably from 0.5 to 4 kg/l/hr and hydrogen to oilratios in the range of from 100 to 2,000 litres of hydrogen per litre ofoil. The weight hourly space velocities (WHSV) in the catalytic dewaxingstep in which the light base oil precursor fraction is processed ispreferably higher than the WHSV in the dewaxing step of the heavy baseoil precursor fraction. More preferably the WHSV in the dewaxing step ofthe light base oil precursor fraction is between 1 and 5 kg/l/hr.

If the dewaxing step and the hydrofinishing step are performed incascade the pressure level in both steps in suitably of the same order.Because higher pressures are preferred in the hydrofinishing step inorder to obtain a base oil having the desired properties the dewaxingstep is suitably also performed at these higher pressures, even though amore selective dewaxing could have been achieved at lower pressures. Ifno hydrofinishing step is required, as has been found to be the case forthe dewaxed oil obtained from the light base oil precursor fraction toprepare for example the spindle oil base oil grade, a lower catalyticdewaxing pressure can advantageously be applied. Suitable pressures arefrom 15 to 100 bar and more suitably from 1.5 to 6.5 MPa.

The hydrotreating step (e) also referred to as a hydrofinishing step isto improve the quality of the dewaxed fraction. In this step lube rangeolefins are saturated, heteroatoms and colour bodies are removed and ifthe pressure is high enough residual aromatics are saturated. Preferablythe conditions are so chosen to obtain a base oil grade comprising morethan 95 wt % saturates and more preferably such that a base oil isobtained comprising more than 98 wt % saturates. The hydrofinishing stepis suitably carried out in cascade with the dewaxing step of the heavybase oil precursor fraction.

The hydrofinishing step is suitable carried out at a temperature between230 and 380° C., a total pressure of between 1 to 25 MPa and preferablyabove 10 MPa and more preferably between 12 and 25 MPa. The WHSV (Weighthourly space velocity) ranges from 0.3 to 10 kg of oil per litre ofcatalyst per hour (kg/l.h).

The hydrofinishing or hydrogenation catalyst is suitably a supportedcatalyst comprising a dispersed Group VIII metal. Possible Group VIIImetals are cobalt, nickel, palladium and platinum. Cobalt and nickelcontaining catalysts may also comprise a Group VIB metal, suitablymolybdenum and tungsten.

Suitable carrier or support materials are low acidity amorphousrefractory oxides. Examples of suitable amorphous refractory oxidesinclude inorganic oxides, such as alumina, silica, titania, zirconia,boria, silica-alumina, fluorided alumina, fluorided silica-alumina andmixtures of two or more of these.

Suitable hydrogenation catalysts include those catalysts comprising asone or more of nickel (Ni) and cobalt (Co) in an amount of from 1 to 25percent by weight (wt %), preferably 2 to 15 wt %, calculated as elementrelative to total weight of catalyst and as the Group VIB metalcomponent one or more of in an amount of from 5 to 30 wt %, preferably10 to 25 wt %, calculated as element relative to total weight ofcatalyst. Examples of suitable nickel-molybdenum containing catalyst areKF-847 and KF-8010 (AKZO Nobel) M-8-24 and M-8-25 (BASF), and C-424,DN-190, HDS-3 and HDS-4 (Criterion). Examples of suitablenickel-tungsten containing catalysts are NI-4342 and NI-4352(Engelhard), C-454 (Criterion). Examples of suitable cobalt-molybdenumcontaining catalysts are KF-330 (AKZO-Nobel), HDS-22 (Criterion) andHPC-601 (Engelhard).

For hydrocracked feeds containing low amount of sulphur, as in thepresent invention, preferably platinum containing and more preferablyplatinum and palladium containing catalysts are used. The total amountof these noble Group VIII metal component(s) present on the catalyst issuitably from 0.1 to 10 wt %, preferably 0.2 to 5 wt %, which weightpercentage indicates the amount of metal (calculated as element)relative to total weight of catalyst.

Preferred supports for these palladium arid/or platinum containingcatalysts are amorphous silica-alumina, whereby more preferably thesilica-alumina comprises from 2 to 75 wt % of alumina. Examples ofsuitable silica-alumina carriers are disclosed in WO-A-9410263. Apreferred catalyst comprises an alloy of palladium and platinumpreferably supported on an amorphous silica-alumina carrier of which thecommercially available catalysts C-624 and C-654 of Criterion CatalystCompany (Houston, Tex.) are examples.

In step (f) the two or more base oil grades and optionally a gas oilcomprising fraction are isolated from the light base oil precursorfraction from step (d) and the hydrotreated oil from step (e). The baseoils and the optional gas oil comprising fraction are preferablyisolated from a mixture of these streams. This is advantageous becauseany compounds present in the heavy base oil precursor fraction which areconverted in step (d) to a boiling range of a lighter base oil gradewill then contribute to the base oil yield of said lighter base oilgrade.

Because the gas oil product as obtained as described above has beensubjected to a catalytic dewaxing step a fuel product is obtained havinga very low content of aromatics and sulphur in combination withexcellent low temperature properties. Especially a gas oil may beobtained in step (d) having a very low sulphur content of below 10 ppm,a low aromatics content of below 0.1 mmol/100 grams, excellent a coldflow properties like a pour point of below −30° C. and a cold filterplugging point of below −30° C. The gas oil also has excellent lubricityproperties. This makes such a gas oil especially an excellent refineryblending component to blend low sulphur gas oil. The gas oil may also beused as a drilling mud fluid component, an electrical oil, a cuttingoil, an aluminium rolling oil or as a fruit spray oil.

Step (f) may be performed by withdrawing products along a distillationcolumn operating at near vacuum conditions as well known to the skilledperson. Preferably so-called side-strippers are used to isolate the baseoil products. Intermediate fractions may also be withdrawn in order tomeet the volatility requirements of the desired base oil grades.Suitably before the above low pressure distillation step a higherpressure distillation step, at about atmospheric conditions, may beperformed in order to separate any naphtha, kerosene and gas oilfractions, separately or as a mixture, from the dewaxed oil. Thesemiddle distillate fractions may be used as such or recycled to step (b)such that a mixture of dewaxed and hydrocracked middle distillate fuelsare obtained. Thus in step (f) gaseous tops, a liquid tops comprisingthe above middle distillates, and various base oil grades, as forexample a spindle oil, a light machine oil and a medium machine oil areobtained in the final distillation of step (f).

In the context of the present invention terms as spindle oil, lightmachine oil and medium machine oil will refer to base oil grades havingan increasing kinematic viscosity at 100° C. and wherein the spindle oiladditionally has a maximum volatility specification. The advantages ofthe present process are achieved for any group of base oils having suchdifferent viscosity requirement and volatility specification. Preferablya spindle oil is a light base oil product having a kinematic viscosityat 100° C. of below 5.5 cSt and preferably above 3.5. The spindle oilcan have either a Noack volatility, as determined by the CEC L-40-T87method, of preferably below 20% and more preferably below 18% or a flashpoint, as measured according to ASTM D93, of above 180° C. Preferablythe light machine oil has a kinematic viscosity at 100° C. of below 9cSt and preferably above 6.5 cSt and more preferably between 8 and 9cSt. Preferably the medium machine oil has a kinematic viscosity at 100°C. of below 14 cSt and preferably above 10 cSt and more preferablybetween 11 and 13 cSt. The corresponding base oil grade can have aviscosity index of between 95 and 120. Gas oil as obtained in theprocess according the invention will boil typically from 150 and 370° C.and will have a T90wt % of between 340-400° C.

The process of the present invention is further illustrated by FIG. 1.FIG. 1 shows a hydrocarbon feed line (1) to hydrocracker (2). Thehydrocrakate (3) is separated into a naphtha (5), kerosene (6), a gasoil (7) a bottoms fraction (8) in distillation column (4). The bottomsfraction or full range residue (4) is split into a light base oilprecursor fraction (10) and a heavy base oil precursor fraction (11) indistillation column (9). The light base oil precursor fraction (10) isdewaxed in dewaxing reactor (12) yielding a dewaxed oil (16; “seconddewaxed oil”). The heavy base oil precursor fraction (11) is dewaxed indewaxing reactor (13). The dewaxed oil (15; “first dewaxed oil”) ishydrotreated in hydrofinishing reactor (14) yielding a dewaxed andhydrotreated oil (17). Oils (16) and (17) are combined. Hydrogen (19) isseparated in separator (18) and recycled to the dewaxing units (12) and(13) after adding fresh hydrogen (20). The oil (21) is subsequentlyseparated into a low boiling fraction (26), a spindle oil grade (23), alight machine oil grade (24) and a medium machine oil grade (25) isdistillation column (22). The fraction (26) is recycled to the work-upsection of the hydrocracker (2) in order to isolate the valuable fuelsfractions.

1. A process for making a base oil product, said process comprises thefollowing steps: (a) hydrocracking a mineral crude derived feed, therebyobtaining an effluent; (b) distilling said effluent as obtained in step(a) into at least one middle distillates product and a residue boilingsubstantially above 340° C.; (c) separating, said residue into a lightbase oil precursor fraction and a heavy base oil precursor fraction; (d)reducing the pour point of said heavy base oil precursor fraction bycatalytic dewaxing to obtain a first dewaxed oil and reducing the pourpoint of said light base oil precursor fraction by catalytic dewaxing toobtain a second dewaxed oil; (e) hydrotreating said first dewaxed oil asobtained from the catalytic dewaxing of said heavy base oil precursorfraction in step (d) to provide a hydrotreated oil; and (f) isolatingfrom the second dewaxed oil and from the hydrotreated oil two or morebase oil grades.
 2. A process according to claim 1, wherein more than 80wt % of the residue boils above 340° C. and wherein between 10 and 40 wt% of the combined first dewaxed oil and second dewaxed oil boils in theheavy gas oil range of between 350° C. to 400° C.
 3. A process accordingto claim 2, wherein between 20 and 40 wt % of the heavy base oilprecursor fraction as obtained in step (c) is recycled to step (a).
 4. Aprocess according to claim 1, wherein the 10 wt % recovery point of theheavy base oil precursor fraction as obtained in step (c) is between 420and 550° C.
 5. A process according to claim 4, wherein the 10 wt %recovery point of the heavy base oil precursor fraction as obtained instep (c) is between 440 and 520° C.
 6. A process according to claim 1,further comprising adding a partly isomerized paraffin wax as obtainedin a Fischer-Tropsch process and boiling in the heavy base oil precursorfractions boiling range to said heavy base oil precursor fraction priorto its catalytic dewaxing.
 7. A process according to claim 1, whereinthe weight hourly space velocity in the catalytic dewaxing step (d) forprocessing the light base oil precursor fraction is higher than theweight hourly space velocity in the catalytic dewaxing step (d) forprocessing the heavy base oil precursor fraction.
 8. A process accordingto claim 7, wherein the weight hourly space velocity in the catalyticdewaxing step (d) for processing the light base oil precursor fractionis between 1 and 5 kg/l/hr.
 9. process according to claim 8, wherein thepressure at which the light base oil precursor fraction is dewaxed instep (d) is between 15 and 65 bars and the pressure at which the heavybase oil precursor fraction is dewaxed is between 100 and 250 bars. 10.A process according to claim 9, wherein step (f) is performed on amixture of the second dewaxed oil as obtained when processing the lightbase oil precursor fraction and the hydrotreated oil.
 11. A process formaking multiple grades of base oil products, wherein said processcomprises: hydrocracking a vacuum gas oil to yield a hydrocrackereffluent; separating said hydrocracker effluent into a middle distillatefraction and a residue fraction of which said residue fraction apredominant portion thereof boils above 340° C.; separating said residuefraction into a light base oil precursor fraction and a heavy base oilprecursor fraction; reducing the pour point of said heavy base oilprecursor fraction by catalytically dewaxing thereof to yield a firstdewaxed oil; reducing the pour point of said light base oil precursorfraction by catalytically dewaxing thereof to yield a second dewaxedoil; hydrotreating said first dewaxed oil to provide a hydrotreated oil;and separating said hydrotreated oil and said second dewaxed oil into atleast two base oil products of different base oil grades.
 12. A processas recited in claim 11, wherein more than 80 wt % of said residuefraction has a boiling temperature above 340° C.
 13. A process asrecited in claim 12, wherein from between 10 to 40 wt % of the total ofsaid hydrotreated oil and said second dewaxed oil boils in the heavy gasoil boiling range of from 350° C. to 400° C.
 14. A process as recited inclaim 13, wherein the catalytic dewaxing process conditions of the stepfor reducing the pour point of said light base oil precursor fractionincludes a weight hourly space velocity (WHSV) in the range of from 1 to5 kg/l/hr and a second catalytic dewaxing pressure in the range of from15 to 65 bars, and the catalytic dewaxing process conditions of the stepfor reducing the pour point of said heavy base oil precursor fractionincludes a weight hourly space velocity (WHSV) in the range of from 0.2to 5 kg/l/hr and a first catalytic dewaxing pressure in the range offrom 100 to 250 bars.